A luminaire as well as a system of luminaires of the types described in the opening paragraph are known as such. For example, the patent application with publication number WO2012/159633 shows in its FIG. 1 schematically an intelligent lamp for outdoor application comprising a sensor unit, a calculation unit, a communication unit and a lamp housing with a light source and related optics. Table 1 of this patent publication describes in detail a number of different weather types and/or road conditions measured by the sensor and the patterns of operation of the lamp based on these whether types.
The mentioned patent publication however has the clear problem in that it fails in disclosing a clear technical teaching how various weather types and/or road conditions can be distinguished by the sensor.
It is an object of the invention to overcome or at least reduce the technical problem present in the known (system of) luminaires. More particularly, the invention aims at providing a—preferably simple—way of measuring road- and/or weather-related information based on which the luminaire may adjust its light output in order to illuminate the road in an optimal manner.